Rapid self-healable poly(ethylene glycol) hydrogels formed by selective metal–phosphate interactions

Abstract

Rapid self-healable and biocompatible hydrogels were prepared using the selective formation of metal-ligand interactions between selected metal ions and phosphate end groups of poly(ethylene glycol) (PEG). The phosphate-terminated branch of PEG was synthesized via a substitution reaction of the hydroxyl end groups using phosphoryl chloride. The gelation and gel properties including rheological properties can be tuned by the careful selection of metal ions, branch numbers, and temperature. Especially, the gels rapidly formed by trivalent metal ions such as Fe(3+), V(3+), Al(3+), Ti(3+), and Ga(3+) have relatively small ionic radii. The ligand substitution rates also affected the repeatable autonomic healing ability. We have also demonstrated a gel-sol/sol-gel transition by switching the redox states of Fe(3+)/Fe(2+) ions. Learning from biological systems, the proposed phosphate-metal ion based self-healable hydrogels could become an attractive candidate for various biomedical and environmental applications.

An Intriguing Method for Fabricating Arbitrarily Shaped “Matreshka” Hydrogels Using a Self-Healing Template

“…All ions successfully gelated the PEG-phos; however, the gelation time was significantly affected by ion species. For example, gelation quickly occurred within seconds for Fe 3+ , Ti 3+ , and Ga 3+ , while it took 40 s for V 3+ , as previously reported [25]. These phenomena have been explained by their coulomb potential values and water substitution rates [25].…”

“…The combination of catechol–Fe 3+ bonds have also been known to reconstruct bonds spontaneously [24]. We have recently reported bio-inspired metallo-supramolecular hydrogels using phosphate-terminated poly(ethylene glycol) (PEG-phos) and various trivalent metal ions, such as Fe 3+ , V 3+ , Al 3+ , Ti 3+ , and Ga 3+ [25]. In this study, we report a new hydrogel fabrication method utilizing our previously developed self-healing hydrogel as a template.…”

Self-Healing Hydrogels Formed by Complexation between Calcium Ions and Bisphosphonate-Functionalized Star-Shaped Polymers

“…This is comparable to other star-shaped PEG self-healing hydrogels reported in the literature. 10,15,29,30 Furthermore, the damping factor returned to its original level almost instantaneously for every cycle. A similar self-healing capability was observed for all P(8)20-AA gelation conditions tested irrespective of the polymer or Ca 2+ concentrations (see Fig.…”

Novel Multi-Stage Three-Dimensional Deployment Employing Ionoprinting of Hydrogel Actuators

“…The easily accessible oxidation states of iron have been used by different research groups to induce variable strength ionic crosslinking for shape-memory, self-healing, and sol-gel transition [5,[7][8][9][10]. Iron(III) cations can been described as "hard" cations binding strongly to oxygen atoms in negatively charged ligands over others; while iron(II) cations are "soft" cations which prefer to bind to neutrally charged ligands [11].…”